KLK3 and neoplasm: Using a PSA promoter (PSAP) driven EGFP lentiviral tracing reporter, we have recently provided evidence that the undifferentiated (PSA−/lo) PCa cell population harbors long-term tumor-propagating PCSCs that preferentially express stem cell-associated genes and can self-renew to generate PSA+ PCa cells by asymmetric cell division [13].